1. Field of the Invention
The present invention relates to a sheet feed device for clamping and feeding a sheet, such as a sheet feed device used for an image forming apparatus such as a copying machine and a laser beam printer.
2. Description of the related Art
Conventionally, the image forming apparatus such as a copying machine and a laser beam printer include the configuration having a door to be opened or closed with respect to the apparatus main body at the time of for example the paper jamming process. In order to facilitate the paper jamming process, there is a configuration of opening the sheet feeding path (sheet clamping) by separating a feed roller pair for clamping and feeding the sheet according to the door opening and closing operation, that is, by separating the rollers comprising the roller pair.
As to the configuration of the door to be opened or closed, for example, one to be opened or closed around the lower side of the door comprising the apparatus side surface exterior as the rotation center, one to be slid and moved in the right and left direction as it is (substantially parallel to the apparatus installation surface), or the like can be presented. For preventing damage of the feed roller pair to be moved away at the time of releasing clamping of the sheet as mentioned above, a configuration of opening or closing by moving parallel the other roller with respect to one roller in the roller axis direction is preferable.
For example, as shown in FIG. 12, there is one having one roller 5 out of a feed roller pair 5, 10 provided between an apparatus main body front side plate 8 and an apparatus main body rear side plate 9 disposed on the side of a door 91 to be opened or closed with respect to the apparatus main body. The one roller 5 provided on the door 91 side is forced to the other roller 10 side on the apparatus main body side by pressure springs 4a, 4b for obtaining the feeding force. Therefore, in a state with the door 91 opened, the roller 5 on the door 91 side is disposed at a position with a stopper part 3a (3b) of a roller bearing 3 for supporting the one roller 5 and a stopper part 51a (51b) of a door 51 are engaged according to the urging force of the pressure springs 4a, 4b. According to the configuration, since the one roller 5 is pulled out substantially parallel to the other roller 10 according to the opening and closing operation (slide movement) of the door 91 at the time of the paper jamming process, the paper jamming process can be executed by releasing the clamping state of the feed roller pair 5, 10 without damaging the rollers 5, 10.
However, in the case the rotation shaft of the door to be opened or closed with respect to the apparatus main body is provided on the lower side of the door, or in the case the door is slid and moved in the right and left direction in the above-mentioned conventional examples, unless the grip for opening or closing the door is disposed in the substantial center of the door, the opening and closing operation cannot be executed smoothly, and thus a problem of the poor operability is involved.
Furthermore, in the case the rotation axis of the door is provided in the lower side of the door, at the time of opening or closing the door, the user should open the door while supporting the same with the hands, and a problem of the poor operability is involved.
Moreover, in the case the door is slid and moved in the right and left direction as it is, the door can hardly be slid and moved smoothly unless the front and rear sides of the door are well balanced (in the direction substantially orthogonal to the moving direction), and thus a problem of the poor operability is involved. Furthermore, for sliding and moving the door easily and smoothly, a problem of the complication of the mechanism for sliding and moving the door is involved.
Therefore, in order to improve the user operability, as shown in FIG. 11, a configuration of providing the door 51 provided with the rotation axis 51a on the apparatus deeper side for opening and closing the door 51 from the apparatus front side to the apparatus deeper side, can be considered. However, in the case of the configuration of opening and closing by separating the feed roller pair 5, 10 as in the above-mentioned conventional example, using the door 51 shown in FIG. 11, the following problem is involved.
As shown in FIG. 11, the one roller 5 provided on the door 51 side out of the feed roller pair 5, 10 provided between the apparatus main body front side plate 8 and the apparatus main body rear side plate 9 is forced to the other roller 10 side on the apparatus main body side by the pressure springs 4a, 4b for obtaining the feeding force. Therefore, in a state with the door 51 opened, the roller 5 on the door 51 side is disposed at a position with the stopper part 3a (3b) of the roller bearing 3 for supporting the one roller 5 and the stopper part 51a (51b) of the door 51 engaged by the urging force of the pressure springs 4a, 4b. Therefore, by closing the door 51 in this state, since the deeper side end part 5a of the roller 5 on the door 51 side is contacted with the circumferential surface of the roller 10 on the apparatus main body side during the closing operation, there is the risk of damaging the circumferential surface of the roller 10 on the apparatus main body side or the deeper side end part 5a of the roller 5 on the door 51 side.
For example, in the case the other roller 10 of the feed roller pair is an intermediate transfer belt for bearing a toner image (the reference numeral 152 in FIG. 11 and FIG. 12), a photosensitive drum, or the like, a problem of causing the image deterioration is involved. Or in the case the deeper side end part of the one roller 5 of the feed roller pair is a gear for transmitting the driving force, there is the risk of causing breakage of the members.